Remove declaration of not implemented functions
Remove declaration of not implemented functions

mpd_sendPlaylistClearCommand, mpd_sendPlaylistAddCommand,
mpd_sendPlaylistMoveCommand and mpd_sendPlaylistDeleteCommand were declared in
mpd/client.h but were not implemented anywhere.

jagleeso/libmpdclient,yusiwen/libmpdclient,psych0tik/libmpdclient2,OpenInkpot-archive/iplinux-libmpdclient,jagleeso/libmpdclient,sl0th/libmpdclient,yusiwen/libmpdclient,cmende/libmpdclient,psych0tik/libmpdclient2,sl0th/libmpdclient,sl0th/libmpdclient,jwise/libmpdclient,OpenInkpot-archive/iplinux-libmpdclient,yusiwen/libmpdclient,jagleeso/libmpdclient,jwise/libmpdclient,cmende/libmpdclient,jwise/libmpdclient,cmende/libmpdclient